The present invention relates generally to a diskette incorporating a permanent magnet generator, and more particularly to a diskette incorporating a permanent magnet generator, and a permanent magnet generator that is incorporated in a diskette used by inserting into a floppy disk drive, and when a memory is installed in the diskette, serves as a power source for the memory to input and output data in the memory.
Medical information, such as personal medical checkup results, is stored in an IC card, from which medical institutions can retrieve such information for use in the treatment of the patient, and can store the contents of his case records in the card. Plans are also now under way to use IC cards as electronic cash. Under the plans, data on a customer""s bank account, password, and his bank balance, if necessary, are stored in an IC card, by means of which payment is made on-line every time the customer buys a product.
It has been proposed that an enormous amount of video information handled by a digital camera should be stored in a flash memory that has a capacity as large as a couple of megabytes to 10 megabytes. A flash memory in which the video information is taken by a digital camera can be connected to a personal computer for subsequent video processing. The use of a flash memory to record the video information taken by a digital camera may eliminate an additional external memory unit, such as MOs.
The widespread use of IC cards or flash memories, as discussed above, has been deterred by the need for special input/output (I/O) devices dedicated for such media. Since most commonly used I/O devices for personal computers are floppy disk drives, particularly 3.5xe2x80x3 floppy disk drives, the use of 3.5xe2x80x3 floppy disks as an I/O device for IC cards and flash memories could spur their proliferation. In fact, adapters that can be inserted or incorporated in 3.5xe2x80x3 floppy disk drives have already been proposed. A conventional type of 3.5xe2x80x3 floppy disk drive has magnetic head to read and write information from and into a 3.5xe2x80x3 diskette and a drive shaft to cause the diskette to rotate at 300 rpm, but it has no power feeding terminals. In diskette-shaped adapters, as discussed above, a button battery is incorporated as a power source for the built-in CPU. A battery, which depletes as it is used, has to be replaced with a new one every four to five months at the longest.
Introduction of a 3.5xe2x80x3 floppy disk in which a generator is incorporated and driven by the rotation of the drive shaft of the 3.5xe2x80x3 floppy disk drive would prove very useful, giving momentum to the proliferation of IC cards and similar media. In fact, the concept of incorporating a generator in a 3.5xe2x80x3 diskette has already been proposed in Published Examined Japanese Patent Application No. Hei-7(1995)-86912 and Tokuhyo Hei-7(1995)-500238, the published Japanese translation of PCT international publication for patent application.
Published Examined Japanese Patent Application No. Hei-7(1995)-86912 discloses that a generator is incorporated in a 3.5xe2x80x3 diskette, and that the generator has a rotor, a stator and a regulator, but its detailed construction is not disclosed. Tokuhyo Hei-7(1995)-500238 discloses a generator incorporated in a 3.5xe2x80x3 diskette having a permanent magnet that rotates with a hub, which is caused to rotate by the drive shaft of a floppy disk drive. This permanent magnet is of a cylindrical shape, magnetized in the axial direction so that multiple magnetic poles are provided on the end face of the cylinder. The magnetic poles of a stator yoke are disposed in such a manner as to sandwich the cylindrical permanent magnet, and a stator coil is provided between the stator yokes on both sides of the cylindrical permanent magnet. Another example is also disclosed in which magnetic poles are provided on the circumferential surface of the cylindrical permanent magnet. In this example, the magnetic poles of the stator yoke are of a claw pole shape.
In this way, these documents state a permanent magnet type generator incorporated in a 3.5xe2x80x3 diskette, but it is unknown how much output can be produced with such a generator because they do not disclose the material of permanent magnet suitable for use in such a generator, and the detailed construction of the rotor and stator.
Now, let us consider a permanent magnet generator of a size that can be incorporate in a 3.5xe2x80x3 floppy disk, as disclosed in Tokuhyo Hei-7(1995)500238, where the cylindrical permanent magnet is magnetized in such a manner that multiple magnetic poles are provided on the end face of the cylinder. In this case, stator magnetic poles are disposed on both sides of the cylinder end face via small magnetic gaps. Since the allowable thickness of a generator in a diskette is 2.0 to 2.5 mm, the thickness of the permanent magnet is only 0.5 to 0.8 mm at most. Even when a material having a large coercive force is used for a magnet with such a short distance between-magnetic poles, only a small magnetomotive force can be expected. Even if magnetomotive force is increased by increasing the thickness of the magnet, the allowable thickness of the stator magnetic poles is reduced, making it difficult to pass sufficient magnetic flux in them.
In a permanent magnet generator where magnetic poles are provided on the circumferential surface of the cylindrical permanent magnet and the claw pole type stator yoke is provided, as disclosed in Tokuhyo Hei-7(1995)-500238, the end yoke of both claw pole type magnetic poles is provided facing each other within the allowable thickness of 2.0 to 2.5 mm for the generator, and a stator winding is provided between the end yoke. Since a sufficient number of winding turns cannot be provided within the allowable length of no more than 1 mm for the stator winding. Thus, a generator having a low output voltage would result.
In order to realize a generator having as high an output as possible and as low distortion as possible, it is necessary to dispose rotor magnetic poles on the circumferential surface of the cylindrical permanent magnet at equal angular intervals, make the number of magnetic poles of the stator yokes equal to the number of magnetic poles of the rotor permanent magnet, and dispose the stator magnetic poles facing the permanent magnet magnetic poles via magnetic gaps of substantially the same size. If a generator of such a construction is to be incorporated in a thin 3.5xe2x80x3 diskette, the teeth of the stator magnetic poles must be extended outward in the radial direction from the stator magnetic poles. When the number of magnetic poles is 12 to 24 and the inside diameter of the stator yoke is 30 mm, the inner circumferential dimensions of the stator yoke given to one magnetic pole is as small as 8 to 4 mm. If stator magnetic poles of a 4-mm width are used, the gaps between the stator magnetic poles is not more than 4 mm. The gaps between the magnetic pole teeth, however, become considerably larger along the outer circumference of the stator magnetic poles, beyond which the teeth of the stator magnetic poles extend outward in the radial direction.
Since the allowable thickness of a generator is 2.0 to 2.5 mm, as described above, the allowable thickness of the stator coil is 0.6 to 0.8 mm on one side if the thickness of the stator magnetic poles is 0.8 mm. No matter how densely a coil is wound on this thin allowable coil thickness, the number of turns of coil cannot be increased too much. On the outer circumference of the stator magnetic pole where the gaps between the magnetic pole teeth are large, the gaps between the coils will have to be increased, producing a large dead space around them. This is contrary to the purpose of the present invention to reduce space as much as possible when a permanent magnet generator is incorporated in a small diskette.
It is therefore an object of the present invention to provide a diskette incorporating a thin permanent magnet generator that can eliminate dead space within the generator and produce a sufficient output.
It is another object of the present invention to provide a diskette incorporating a permanent magnet generator having such a construction that even when the relative position of the diskette to the floppy disk drive is shifted, the entire generator can self-adjust its position with respect to the diskette incorporating the generator by aligning with the drive shaft of the floppy disk drive.
It is a further object of the present invention to provide a diskette incorporating a permanent magnet generator in which leakage flux from the generator is reduced to such an extent as to prevent leakage flux from adversely affecting the IC card or magnetic card inserted into the diskette, in parallel with the generator.
It is still a further object of the present invention to provide a thin permanent magnet generator that can be incorporated in a diskette and has such a construction that dead space within the generator can be eliminated and a sufficient output can be obtained.
It is still a further object of the present invention to provide a permanent magnet generator that has a thin and easy-to-assemble construction.
It is still a further object of the present invention to provide a permanent magnet generator that can ensure smooth rotation and stable output even with a low-torque drive source, such as a 3.5xe2x80x3 floppy disk drive, by reducing cogging torque in the generator.
A diskette incorporating a permanent magnet generator according to the present invention comprises
a diskette case and a permanent magnet generator provided in the diskette case; the permanent magnet generator comprising
(1) a rotor having a ring-shaped permanent magnet that can rotate, together with a hub of the diskette; the permanent magnet having a plurality of rotor magnetic poles arranged on the circumferential surface thereof; the magnetic poles having alternately different polarities in the circumferential direction, and
(2) a stator having a plurality of magnetic pole teeth made of soft magnetic material; the magnetic pole teeth
(I) having on one end thereof stator magnetic poles that can face the aforementioned rotor magnetic poles provided on the circumferential surface via a magnetic gap,
(II) extending outward from the stator magnetic poles, with stator coils wound thereon, and
(III) the ends opposite to the stator magnetic poles of the stator magnetic pole teeth and the ends opposite to the stator magnetic poles of the adjoining magnetic pole teeth are connected to each other by a back yoke,
where the rotor and the stator are formed into a flat plate shape as a whole, and the thickness of the stator magnetic poles in the axial direction is smaller than the axial thickness of the permanent magnet.
The diskette, described above, incorporating a permanent magnet generator according to the present invention is desired to have such a construction that 12 to 24 magnetic poles are provided on the circumferential surface of the rotor permanent magnet at substantially equal angular intervals; each magnetic pole of the stator magnetic pole teeth being provided in such a manner as to be able to face each magnetic pole of the rotor.
The diskette, described above, incorporating a permanent magnet generator according to the present invention is desired to have such a construction that 12 to 24 magnetic poles are provided on the circumferential surface of the rotor permanent magnet at substantially equal angular intervals; each magnetic pole of the stator magnetic pole teeth being provided in such a manner as to be able to face each magnetic pole of the rotor magnetic poles, except for at least one magnetic pole.
The diskette, described above, incorporating a permanent magnet generator according to the present invention is desired to have such a construction that the magnetic pole teeth of the permanent magnet generator
(I) have on one end thereof stator magnetic poles provided in such a manner as to face the rotor magnetic poles, except for at least one pole, and disposed at substantially equal angular intervals on the circumference thereof, except for the portion facing at least the one pole, and
(II) extend outward from the stator magnetic poles, with stator coils wound thereon, and
(III) the ends opposite to the magnetic poles of the magnetic pole teeth having the stator magnetic poles provided at substantially equal angular intervals are connected to each other via a back yoke made of soft magnetic material.
A diskette incorporating a permanent magnet generator according to the present invention comprises a diskette case and a permanent magnet generator provided in the diskette case;
The permanent magnet generator comprising
(1) a rotor having a ring-shaped permanent magnet that can rotate, together with a hub of the diskette; the permanent magnet having a plurality of rotor magnetic poles arranged on the circumferential surface; the magnetic poles having alternately different polarities in the circumferential direction and
(2) a stator having a plurality of magnetic pole teeth made of soft magnetic material; each of the magnetic pole teeth
(I) having adjacent to one end thereof stator magnetic pole portions extending in the radial direction from the positions at which the stator magnetic poles can face the aforementioned rotor magnetic poles provided on the circumferential surface via a magnetic gap,
(II) continuously extending outward from the stator magnetic pole portions, and having magnetic pole tooth portions on which stator coils are wound, and
(III) forming at least one block, with the magnetic pole tooth portions in each block disposed in substantially parallel with each other and the adjoining stator coils disposed close to each other, and the ends opposite to the magnetic poles of the magnetic pole teeth and the ends opposite to the magnetic poles of the adjoining magnetic pole teeth connected to each other by a back yoke,
wherein the rotor and the stator are formed into a flat plate shape as a whole; the thickness of the stator magnetic poles in the axial direction is smaller than the thickness of the permanent magnet in the axial direction.
The diskette, described above, incorporating a permanent magnet generator according to the present invention is desired to have at least four magnetic pole teeth in the aforementioned block.
The diskette, described above, incorporating a permanent magnet generator is desired to have such a construction that the intervals of the magnetic pole teeth disposed in substantially parallel in the aforementioned block are unequal. And the number of block can be one.
In the diskette incorporating a permanent magnet generator according to the present invention, a space for inserting a memory card can be provided within the aforementioned diskette case. In this diskette, as the space for a memory card is at least partly overlapped with the permanent magnet generator, at least part of the boundary wall may be a magnetic shield plate. Furthermore, the boundary wall may be used as a housing for the permanent magnet generator.
In the diskette incorporating a permanent magnet generator according to the present invention, any of a diskette input/output terminal, a card contact terminal, and a memory card inserting space can be provided at least partially between the stator magnetic pole teeth that are not connected to each other by a back yoke.
In the diskette incorporating a permanent magnet generator according to the present invention, a holding mechanism that can absorb the misalignment of the permanent magnet generator with respect to the diskette case can be provided within the diskette case.
The diskette incorporating a permanent magnet generator according to the present invention is desired to have such a construction that the adjoining stator magnetic poles facing the permanent magnet at the tips of the stator magnetic pole teeth are connected to each other by an inner yoke. The inner yoke connecting the adjoining stator magnetic poles at the tips of the magnetic pole teeth is desired to have a thinnest thickness at the central part between the adjoining stator magnetic poles. The inner yoke connecting the adjoining stator magnetic poles at the tips of the magnetic pole teeth is desired to be such that the cross-sectional area of the central part of the inner yoke between the adjoining stator magnetic poles is smaller than the cross-sectional area of the magnetic pole teeth.
The diskette, described above, incorporating a permanent magnet generator according to the present invention is desired to have such a construction that the hub of the permanent magnet generator can be engaged with the drive shaft of the disk drive unit.
The diskette, described above, incorporating a permanent magnet generator according to the present invention is desired to have such a construction that the diskette may be fitted to the 3.5xe2x80x3 floppy disk drive.
The diskette, described above, incorporating a permanent magnet generator according to the present invention is desired to have such a construction that the rotor permanent magnet has the axis of easy magnetization in the radial direction. The diskette incorporating a permanent magnet generator according to the present invention is desired to have such a construction that the rotor permanent magnet has the axis of easy magnetization in the direction in which the adjoining magnetic poles of different polarities on the circumference thereof are connected. The rotor permanent magnet may be a sintered NdFeB magnet. In the diskette incorporating a permanent magnet generator according to the present invention, the rotor permanent magnet may be a permanent magnet produced by bonding powdered NdFeB using a binder.
A permanent magnet generator incorporated in a diskette according to the present invention comprises
(1) a rotor having a ring-shaped permanent magnet that can rotate, together with the hub; the permanent magnet having a plurality of rotor magnetic poles arranged on the circumferential surface; these magnetic poles having alternately different polarities in the circumferential direction,
(2) a stator having a plurality of magnetic pole teeth made of soft magnetic material; the magnetic pole teeth
(I) having one end thereof stator magnetic poles that can face the rotor magnetic poles provided on the circumferential surface via magnetic gaps,
(II) extending outward from the stator magnetic poles, with stator coils wound thereon, and
(III) the ends opposite to the magnetic poles of the stator magnetic poles and the ends opposite to the magnetic poles of the adjoining magnetic pole teeth being connected to each other via a back yoke,
wherein the rotor and the stator are formed into a flat disk shape as a whole and the thickness of the stator magnetic poles in the axial direction is smaller than the thickness of the permanent magnet in the axial direction.
The permanent magnet generator incorporated in a diskette according to the present invention is desired to have such a construction that the magnetic poles the rotor permanent magnet has on the circumferential surface thereof are disposed at substantially equal angular intervals and the number of poles is 12 to 24 poles, and the magnetic poles of the stator magnetic pole teeth are provided in such a manner as to face the rotor magnetic poles.
Alternatively, the permanent magnet generator, described above, incorporated in a diskette according to the present invention is desired to have such a construction that the magnetic poles the rotor permanent magnet has on the circumferential surface thereof are disposed at substantially equal angular intervals and the number of poles is 12 to 24 poles, and the magnetic poles of the stator magnetic pole teeth are provided in such a manner as to face the rotor magnetic poles, except for at least one pole.
The permanent magnet generator, described above, incorporated in a diskette according to the present invention is desired to have such a construction that the stator magnetic pole teeth of the permanent magnet generator
(I) have on one end stator magnetic poles; the stator magnetic poles provided at substantially equal angular intervals on the circumference, except for the portions facing at least one pole, so as to face the rotor magnetic poles, except for at least one pole,
(II) extend outward from the stator magnetic poles, with stator coils wound thereon, and
(III) the ends opposite to the magnetic poles of the magnetic pole teeth having the stator magnetic poles provided at substantially equal angular intervals are connected to each other by a back yoke made of soft magnetic material.
A permanent magnet generator incorporated in a diskette according to the present invention comprises
(1) a rotor having a ring-shaped permanent magnet that can rotate, together with the hub; the permanent magnet having a plurality of rotor magnetic poles arranged on the circumferential surface; these magnetic poles having alternately different polarities in the circumferential direction, and
(2) a stator having a plurality of magnetic pole teeth made of soft magnetic material; the magnetic pole teeth
(I) having adjacent to one end thereof stator magnetic pole portions that extend in the radial direction from the position at which the magnetic pole teeth can face the rotor magnetic poles provided on the circumferential surface via magnetic gaps,
(II) continuously extending outward from the stator magnetic pole portions, having magnetic pole teeth portions on which stator coils are wound, and
(III) the magnetic pole teeth combined into at least one block, with the magnetic pole teeth portions in each block being substantially parallel with each other and the adjoining stator coils being close to each other, and the ends opposite to the stator magnetic poles of the magnetic pole teeth and the ends opposite to the stator magnetic poles of the adjoining magnetic pole teeth being connected to each other by a back yoke,
wherein the rotor and the stator are formed into a flat disk shape as a whole, and the thickness of the stator magnetic poles in the axial direction is smaller than the thickness of the permanent magnet in the axial direction.
The permanent magnet generator, described above, incorporated in a diskette according to the present invention is desired to have at least four magnetic pole teeth in the block.
The permanent magnet generator, described above, incorporated in a diskette is desired to have such a construction that the intervals, of the magnetic pole teeth substantially parallel with each other in the block are unequal. The number of blocks can be one.
The permanent magnet generator incorporated in a diskette according to the present invention is desired to have such a construction that the adjoining stator magnetic poles facing the rotor permanent magnet at the tips of the magnetic pole teeth are connected to each other by an inner yoke. The inner yoke connecting the adjoining stator magnetic poles at the tips of the magnetic pole teeth is desired to have a thinnest thickness at the central part between the adjoining stator magnetic poles. The inner yoke connecting the adjoining stator magnetic poles at the tips of the magnetic pole teeth is desired to be such that the cross-sectional area of the inner yoke at the central part between the adjoining stator magnetic poles is smaller than the cross-sectional area of the magnetic pole teeth. The inner yoke connecting the adjoining stator magnetic poles at the tips of the magnetic pole teeth is desired to be tapered or connected with an arc toward the thinnest part at the central part between the adjoining magnetic poles.
The permanent magnet generator, described above, incorporated in a diskette according to the present invention is desired to have such a construction that the rotor permanent magnet has the axis of easy magnetization in the radial direction.
The permanent magnet generator incorporated in a diskette according to the present invention is desired to have such a construction that the rotor permanent magnet has the axis of easy magnetization in the direction in which the adjoining magnetic poles of different polarities on the circumference are connected to each other. The rotor permanent magnet may be a sintered NdFeB magnet. In the permanent magnet generator incorporated in a diskette according to the present invention, the rotor permanent magnet may be a magnet produced by binding powdered NdFeB by a binder.
The thickness of the magnetic poles of the stator magnetic pole teeth in the axial direction is desired to be more than the thickness in which saturation is reached by the magnetic flux generated by the rotor permanent magnet. The length of the rotor permanent magnet in the axial direction is desired to be no more than 2.0 mm.
The permanent magnet generator according to the present invention is desired to have such a construction that a back yoke made of soft magnetic material having a flat contact surface in the axial direction is fixedly fitted to the axial end face of the ends opposite to the magnetic poles of the magnetic pole teeth to connect the ends opposite to the magnetic poles of the magnetic pole teeth. The back yoke is of a substantially flat ring shape, for example. The back yoke having a flat contact surface in the axial direction is desired to be fixedly fitted to each of the axial end faces of the ends opposite to the magnetic poles of the magnetic pole teeth to connect the ends opposite to the magnetic poles of the magnetic pole teeth. The back yoke may be a plate member of a U-shaped cross section that is fixedly fitted by enclosing and crimping to the radial end portion opposite to the magnetic poles of the magnetic pole teeth to connect the ends opposite to the magnetic poles of the magnetic pole teeth.
The permanent magnet generator according to the present invention may have a bearing between the facing surfaces on which the stator magnetic poles face the rotor permanent magnet. The bearing may be a roller bearing. The bearing may be a layer having a low frictional coefficient. These constructions are preferable detailed construction of the permanent magnet generator disclosed in the present invention.
The hub of the permanent magnet generator can be engaged with the drive shaft of the diskette drive unit. It is desired that a magnetic shield plate is provided at least one side surface of the permanent magnet rotor of the permanent magnet generator according to the present invention.
In a diskette incorporating a permanent magnet generator according to the present invention, the permanent magnet generator is provided in the diskette, and the back yoke is cut off at least at either place of the diskette input/output terminal or the card contact terminal.